1. Field of Invention
The invention relates to a frame for a bicycle, more particularly to a foldable frame for a bicycle.
2. Description of the Related Art
Referring to FIG. 1, a conventional foldable frame 1 for a bicycle is shown to include first and second frame halves 2,8 with connecting end portions 4,5, and a hinge member that has two knuckles connected securely to the connecting end portions 4,5 of the first and second frame halves 2,8, and a pivot shaft 6 extending through the knuckles so as to interconnect pivotally the connecting end portions 4, 5 of the first and second frame halves 2,8 to permit rotation of the first and second frame halves 2,8 relative to each other to a folded position. A locking device is provided to retain the first and second frame halves 2,8 in an unfolded position, thereby preventing relative rotation between the first and second frame halves 2,8.
The connecting end portions 4,5 of the first and second frame halves 2,8 are in the form of complementary stepped sections 401,501. The locking device includes a locking bolt 7 threadedly inserted through the stepped sections 401,501. However, frequent riding on an uneven road surface will result in a vibration force that forces apart the stepped sections 401,501, which in turn will pull the knuckles away from each other in the axial direction of the pivot shaft 6 such that loosening of the hinge member between the first and second frame halves 2,8 may occur.
The main object of this invention is to provide a foldable frame for a bicycle which is clear of the aforesaid disadvantages that are generally associated with the conventional foldable frame.
Accordingly, a foldable frame for a bicycle of the present invention includes a first frame half with a connecting end portion, a second frame half with a connecting end portion, a vertical pivot member, and a locking device. The first and second frame halves are arranged one behind another. The pivot member interconnects pivotally the connecting end portions of the first and second frame halves to permit rotation of the first and second frame halves relative to each other to a folded position. The locking device locks the first and second frame halves on each other, thereby preventing relative rotation between the first and second frame halves. The connecting end portion of the first frame half has a vertical end surface that is perpendicular to a longitudinal direction of the bicycle, an integral upper lateral projection, and an integral lower lateral projection that is located under the upper lateral projection to define a recess therebetween. The upper lateral projection has a horizontal bottom surface. The lower lateral projection has a horizontal top surface. The connecting end portion of the second frame half has a vertical end surface which is perpendicular to the longitudinal direction of the bicycle and which abuts against the vertical end surface of the first frame half so as to prevent relative movement between the first and second frame halves in the longitudinal direction. The vertical end surface of the second frame half is formed with an integral tongue which engages the recess in the first frame half, and which has a horizontal top surface that abuts against the bottom surface of the upper lateral projection of the first frame half, and a horizontal bottom surface that abuts against the top surface of the lower lateral projection of the first frame half so as to prevent relative vertical movement between the first and second frame halves.